STW81101ATR datasheet(35/42 Pages) STMICROELECTRONICS

35 / 42 page

STW81101

Application information

35/42

Figure 25.

LC lumped balun and matching network (MATCH_LC_LUMP_4G.dsn)

The 6.8nH shunt inductor works as a DC feed for one of the open collector terminal as well

as a matching element along with the other components. The 1.1nH series inductors are

used to resonate the parasitic capacitance of the chip.

For an optimum output matching it is recommended to use 0402 Murata or AVX capacitors

and 0403 or 0604 HQ Coilcraft inductors. It is also advisable to use short interconnection

paths to minimize losses and undesired impedance shift.

An alternative topology, which allows for a more broadband matching and balanced to

unbalanced conversion, is shown it Figure 26.

Figure 26.

Microstrip line and lumped matching network (MATCH_4G_HYBRID.dsn)

Those results have been achieved on an FR4 substrate with a thickness of 350um.

By using this topology the STW81101 is capable to deliver an almost flat power to a 50

Ω

load with a return loss grater than 10dB over the whole frequency band (3.3 to 4.4GHz).

For the differential to single conversion the 50 to 100

Ω Johanson balun is recommended

(3700BL15B100).

RFOUTP

RFOUTN

VCC

1.1nH

3.6nH

0.3pF

6.8nH

0.7pF

50 Ohm

3.6nH

0.3pF

1.1nH

0.7pF

3.5nH

2:1

W=16mil

L=400mil

C=0.7pF

L=1.5nH

VCC

RFOUTP

RFOUTN

50Ohm load

C=8pF

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